This invention relates to a metering apparatus for bulk (flowable) material and is of the type having a motor-driven metering screw which, in each operational (metering and filling) cycle, advances material from a downwardly open chute into a package to be filled.
Metering apparatuses of the above type must meet stringent requirements concerning accuracy of metering and operational speed. It is of primary importance to ensure that the specific volume of the material does not change in an uncontrolled manner. The specific volume is significantly affected in the metering apparatus by the air content and by forces to which the material is exposed during operation, such as sudden directional changes, accelerations and decelerations.
Swiss Pat. No. 595,241 discloses a metering apparatus which includes a stirring mechanism for enhancing the flow of the material to the metering screw. It was found that the stirring device may, by mechanical effects, adversely influence the homogenous consistency of delicate bulk material such as flour. In the apparatus disclosed in the above-named Swiss patent, the material flow is directed into the packages by means of a vertically downwardly oriented metering screw. The latter imparts a rotary motion on the material, as a result of which the material stream exiting at the outlet opening has a downwardly increasing cross-sectional area. In lightweight products, in addition, significant dust generation occurs which, in particular, adversely affects the sealing of the packages.